A vehicle may include an electric machine that may provide a propulsion force to the hybrid vehicle. The electric machine may also supply alternating electrical current to external electrical power consumers from time to time. Further, in some examples, the electric machine may not provide propulsion force for the vehicle. In one example, a hybrid vehicle may be parked at a construction site and the engine of the hybrid vehicle may rotate the armature of the electric machine so that the electric machine may supply electric power to electric power consumers that are external or off-board the hybrid vehicle. The engine of the hybrid vehicle may operate at a variety of speeds and loads to meet the electrical power consumption of the electric power consumers. The engine may also be operated with the electric machine to generate electric power for several hours each day. During some engine operating conditions while the engine and the electric machine are operating to generate electrical power, carbon may tend to build on the engine's spark plugs. If the amount of carbon deposited on the engine's spark plugs is greater than a threshold amount, the engine may misfire. On the other hand, carbon may be removed from the engine's spark plugs while the engine and the electric machine are operating to generate electrical power. Whether or not carbon is being deposited on or being removed from spark plugs depends on the speed and load at which the engine is operating. In addition, the amount of carbon deposited or removed from the spark plugs may vary depending on the speed and load at which the engine is operated. Users of the vehicle may notice engine speed changes if the engine begins to misfire and engine emissions may increase if the engine begins to misfire. Therefore, it may be desirable to provide a way of mitigating the possibility of engine misfires.
The inventors herein have recognized the above-mentioned issues and have developed a powertrain operating method, comprising: characterizing each of a plurality of engine operating regions as one or more carbon building regions, one or more carbon removing regions, or one or more carbon neutral regions; measuring an amount of time an engine operates in the one or more of the carbon building regions via a controller while the engine rotates an electric machine that provides power to external power consumers; and adjusting operation of the engine to operate in one or more of the carbon removing regions while the engine rotates the electric machine that provides power to the external power consumers in response to the amount of time exceeding a threshold.
By adjusting operation of an engine that is coupled to an electric machine that provides power to external electrical power consumers, it may be possible to reduce the possibility of engine misfires when supplying power to electrical power consumers. In particular, if the engine is operating at light loads where carbon may accumulate on the engine's spark plugs while electrical power consumers are electrically coupled to an electric machine that is rotated via the engine, engine speed may be increased even though a load that may be provided by the external electrical power consumers has not changed. By increasing the engine speed, spark plug temperatures may increase, thereby oxidizing carbon that may accumulate on the engine's spark plugs so that the possibility of engine misfires may be reduced. In addition, a load that the electric machine provides to the engine may be increased to further reduce the possibility of spark plug fouling. The increased electric machine load may be used to charge an electric energy storage device that is on-board the vehicle so that beneficial work may be generated by increasing the engine load.
The present description may provide several advantages. In particular, the approach may improve engine operation while an engine is being used to generate electrical power. Further, the approach may provide beneficial work when carbon is being removed from engine spark plugs. In addition, the approach provides compensation for times when the engine is operated in carbon removing operating conditions. Further still, the method described herein may be applied to engines that are operated at extended idle conditions, irrespective of if the engine is driving a mechanical load, or a load that generates electrical power, or no external load.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.